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  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 50 Abstracts search results

Document: 

22-124

Date: 

September 1, 2023

Author(s):

Arindam Dey, Tara L. Cavalline, Miras Mamirov, and Jiong Hu

Publication:

Materials Journal

Volume:

120

Issue:

5

Abstract:

The use of recycled concrete aggregates (RCAs) in lieu of natural aggregates improves the sustainability of the built environment. Barriers to the use of RCA include its variable composition, including the residual mortar content (RMC), chemical composition, and its potential to contain contaminants, which can negatively affect the properties of concrete or present environmental concerns. In this study, a rapid, economical method to estimate the RMC and provide the chemical characterization of RCA was developed using a portable handheld X-ray fluorescence (PHXRF) device. Models were developed using reference tests (RMC test based on the thermal shock method and chemical composition from whole-rock analysis) to correlate PHXRF results to measured values. The PHXRF shows strong potential for estimating the RMC and chemical composition of RCA. Paired with locally calibrated reference samples, the test method could be used in laboratory or field applications to characterize RCA and increase its use in bound and unbound applications.

DOI:

10.14359/51738890


Document: 

22-319

Date: 

July 1, 2023

Author(s):

Fayez Moutassem and Samir E. Chidiac

Publication:

Materials Journal

Volume:

120

Issue:

4

Abstract:

A requirement for achieving sustainable concrete structures is to develop a quantitative method for designing concrete mixtures that yields the target rheological properties and compressive strength. Toward this objective, this paper proposes a mathematical model approach to improve the sustainability of the concrete industry. A postulation that packing density, a function of the concrete mixture, provides the link between concrete mixture, rheological properties, and compressive strength was investigated. Rheological models for yield stress and plastic viscosity, and a compressive strength model were adopted with packing density as a central variable. The rheological models employ a cell description that is representative of fresh concrete. The compressive strength model is based on excess paste theory to account for the concrete mixture proportions, gradation of aggregate particles, and porosity. An experimental program was developed to calibrate and test these models. Results revealed that packing density provides a consistent and reliable link, and that the concrete mixture composition can be designed to achieve the target rheological properties and hardened properties and ensure quality control. Consequently, a new mixture proportioning methodology was developed and proposed as an improvement to the ACI 211.1 mixture design method. Furthermore, a case study was conducted to test for the applicability and adequacy of this proposed method. This research outcome, which provides a quantitative approach to design concrete mixtures to meet specific strength requirements and rheology, can also be used to ensure quality control before concrete is cast.

DOI:

10.14359/51738818


Document: 

21-461

Date: 

January 1, 2023

Author(s):

Francesca Lolli, Renee T. Rios, Katelynn Schoenrock, Emily Grubert, and Kimberly E. Kurtis

Publication:

Materials Journal

Volume:

120

Issue:

1

Abstract:

The use of performance-based specifications (PBS) may increase quality and sustainability while lowering project costs through innovations in concrete materials selection and proportioning. A preliminary survey was conducted showing that barriers to implementation for PBS still exist, the main barrier being the enforcement of the specification, followed by cost and time. This study aims to develop guidelines to overcome the identified barriers by presenting a laboratory-scale case study of six concrete mixtures that both conform (one) and do not conform (five) to Georgia Department of Transportation specifications. This case study includes experimental results of mechanical (flexural and compressive strength) and resistivity performance properties, as well as three additional parameters: time, cost, and carbon dioxide (CO2) emissions associated with each mixture design. This study showed that innovation in material use and mixture design can increase durability and performance while reducing the overall project cost and environmental impact.

DOI:

10.14359/51738457


Document: 

22-057

Date: 

January 1, 2023

Author(s):

N. P. Kannikachalam, D. di Summa, R. P. Borg, E. Cuenca, M. Parpanesi, N. De Belie, and L. Ferrara

Publication:

Materials Journal

Volume:

120

Issue:

1

Abstract:

This research focuses on the evaluation of the sustainability of recycled ultra-high-performance concrete (R-UHPC) in a life cycle analysis (LCA) perspective, and with reference to a case study example dealing with structures exposed to extremely aggressive environments. This involves the assessment of the self-healing capacity of R-UHPC, as guaranteed by the R-UHPC aggregates themselves. Recycled aggregates (RA) were created by crushing 4-month-old UHPC specimens with an average compressive strength of 150 MPa. Different fractions of recycled aggregates (0 to 2 mm) and two different percentages (50 and 100%) were used as a substitute for natural aggregates in the production of R-UHPC. Notched beam specimens were pre-cracked to 150 μm using a three-point flexural test. The autogenous self-healing potential of R-UHPC, stimulated by the addition of a crystalline admixture, was explored using water absorption tests and microscopic crack healing at a pre-determined time (0 days, 1 month, 3 months, and 6 months) following pre-cracking. Continuous wet/ dry healing conditions were maintained throughout the experimental campaign. The specimens using R-UHPC aggregates demonstrated improved self-healing properties to those containing natural aggregates, especially from the second to the sixth month. To address the potential environmental benefits of this novel material in comparison to the conventional ones, an LCA analysis was conducted adopting the 10 CML-IA baseline impact categories, together with a life cycle cost (LCC) analysis to determine the related economic viability. Both LCA and LCC methodologies are integrated into a holistic design approach to address not only the sustainability concerns but also to promote the spread of innovative solutions for the concrete construction industry. As a case study unit, a basin for collection and cooling of geothermal waters was selected. This is representative of both the possibility offered, in terms of structural design optimization and reduction of resource consumption, and of reduced maintenance guaranteed by the retained mechanical performance and durability realized by the self-healing capacity of R-UHPC.

DOI:

10.14359/51737336


Document: 

21-482

Date: 

January 1, 2023

Author(s):

Stephen O. Ekolu

Publication:

Materials Journal

Volume:

120

Issue:

1

Abstract:

Major cities worldwide are densely built with concrete structures. Moreover, urban infrastructures partly cause, and are in return adversely impacted by, the urban heat island (UHI) effect that elevates localized temperature, further to the rise caused by the climate change-induced (CCI) impact of CO2 emissions. While the influence of temperature on carbonation is generally well established based on experimental research, there are hardly any analytical engineering methods specifically for evaluating temperature effect on natural carbonation. In the present study, an equation referred to as the temperature correction factor (TCF) submodel, capable of accounting for temperature effect on natural carbonation, was nested into the natural carbonation prediction (NCP) model, then used to conduct the evaluation.

The second aspect of the present study was employment of the TCF submodel for evaluation of CCI temperature rise on natural carbonation. The scope of evaluation covered 130 selected major cities, geographically located globally and strategically representative of the diverse climate regions worldwide. It was found that tropical climate regions exhibit a more significant increase in CCI carbonation progression compared to that of temperate regions. For structural concretes of normal to moderate strengths, CCI carbonation increases from 34 to 46% in tropical regions and by as low as 9.43/0% in cold/subpolar temperate regions. The silver bullet solution to CCI adverse effects is the use of high-strength concretes, which is a conundrum as this measure undermines or negates sustainability principles. Evidently, the projected CCI global temperature rise significantly increases concrete carbonation in major climate zones. Research is needed into the development of counter measures and design provisions for climate resilience of concrete structures.

DOI:

10.14359/51737335


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